As various electronic devices have been reduced in weight in accordance with a reduction in size, a non-contact type, that is, a wireless power charging scheme for charging a battery using magnetic coupling (or inductive coupling) without electrical contact has risen in prominence.
A wireless power charging scheme is a scheme in which charging is performed through the use of electromagnetic induction. A primary coil (transmission coil) is provided in a charger (wireless power transmitting device), a secondary coil (reception coil) is provided in a charge target (wireless power receiving device), and electric power generated according to inductive coupling between the primary coil and the secondary coil is converted into energy to charge a battery.
In a wireless power charging system, charging efficiency of a wireless power charging system is significantly enhanced as core centers of a wireless power transmitting device and a wireless power receiving device are accurately aligned. Thus, in order to obtain ideal charging efficiency, the core centers of the wireless power transmitting device and the wireless power receiving device should be simply and accurately aligned.
In the related art of a wireless power charging system, however, the part of the wireless power transmitting device on which the wireless power receiving device is placed is flat. In addition, core centers of a primary coil and a secondary coil of the wireless power transmitting device and the wireless power receiving device are visually determined and approximately aligned, resulting in low accuracy regarding the core center alignment.
A reception coil of the wireless power receiving device is formed of copper having low resistance to use inductive coupling, and here, a thickness of the reception coil is manufactured to have a numerical value designed according to overall impedance and resistance values.
Also, the wireless power receiving device is manufactured using a flexible printed circuit board process. Thus, a lead portion is required in the reception coil in order to transmit an induced current through inductive coupling.
A related art reception coil has a structure in which lead portions are disposed on upper and lower surfaces of an insulating layer and a via penetrating through the insulating layer electrically connects the lead portions disposed up and down.
In the related art reception coil, the lead portions are formed to have the same thickness as that of the insulating layer of the coil unit to prevent a degradation of electrical characteristics, causing an overall size (thickness) of the reception coil unit to be increased.